Improved rheological characterisation of self-compacting cementitious pastes and concrete by advanced slump flow test analysis

The slump flow test is a widespread, frequently used and standardized test of workability and especially consistency in the field of concrete processing. While good quality information on yield stress can be derived from it, there is a lack of information on viscosity to date. The outlined paper demonstrates, how to derive plastic viscosity from an advanced evaluation of an automated test set up extended by video recordings of the slump flow test. Cementitious pastes and self-compacting concretes are investigated in a systematic study. The new approach for determining viscosity is introduced by evaluating the data from sectional radial flow velocity recordings with a corresponding modelling strategy. The methodology can also be adapted to the conventional slump flow test without additional technical equipment. Finally, the plastic viscosity is derived within defined constraints by calculating an idealised shear rate and shear stress of a flow curve. Furthermore, the influence of the lifting process and mix composition on the accuracy of the test is demonstrated by comparing conventional and automated mini-slump flow tests, which is useful for applying the test in quality control.